Ultra-narrow spectral response of a hybrid plasmonic-grating sensor

TL;DR

This paper presents a hybrid plasmonic-grating sensor with ultra-narrow spectral response, high sensitivity, and broad operational index range, suitable for precise refractometry.

Contribution

It introduces a nanostructured device combining grating modes and surface plasmon resonances with a novel effective index model.

Findings

Spectral response below 0.1 nm

Operates across refractive index 1.3 to 1.56

Works under normal incidence

Abstract

We configure and analyze a nanostructured device that hybridizes grating modes and surface plasmon resonances. The model uses an effective index of refraction that considers the volume fraction of the involved materials, and the propagation depth of the plasmon through the structure. Our geometry is an extruded low-order diffraction grating made of dielectric nano-triangles. Surface plasmon resonances are excited at a metal/dielectric interface, which is separated from the analyte by a high-index dielectric layer. The optical performance of the refractometric sensor is highly competitive in sensitivity and figure of merit (FOM) because of the the ultra-narrow spectral response (below 0.1 nm). Moreover, it is operative within a wide range of the index of refraction (from 1.3 till 1.56), and also works under normal incidence conditions.